This application claims the priority of Application No. 102 58 250.2, filed 13 Dec. 2002, in Germany, the disclosure of which is expressly incorporated by reference therein.
The invention is based on a rear covering part with a tail pipe orifice fastened thereto, for an exhaust system of a motor vehicle, having a bordered passage opening for the tail pipe orifice.
A rear covering part of the above-mentioned type is known from U.S. Patent Document U.S. Pat. No. 2,850,314. It is constructed as a bumper to which a tail pipe orifice is fastened which—viewed in the flow direction of the exhaust gases—first narrows in a transition section and then expands in a fan-shaped manner in an outlet section. The outlet opening of the tail pipe orifice is situated in a passage bore which is provided in the rear covering part. The tail pipe orifice has an inlet opening which communicates with a tail pipe of the exhaust system. The outlet opening is arranged downstream of the inlet opening. The transition section, which is tapered in its cross-section, is arranged in-between. In order to guide cooling air flow through the tail pipe orifice while driving the vehicle, the interior cross-section of the inlet opening is larger than the exterior cross system of the tail pipe of the exhaust system, and the air inlet section of the tail pipe orifice having the inlet opening reaches over the tail pipe and is situated at a radial distance from the tail pipe. Only a connection to the rear covering part is provided for the fastening of the tail pipe. Thus, a heat transmission from the tail pipe of the exhaust system to the tail pipe orifice can take place only by the hot exhaust gas because no contact exists between the tail pipe and the orifice, and a heat conducting connection of materials between the tail pipe orifice and the tail pipe is therefore avoided.
German Patent Document DE 100 25 121 A1 discloses a tail pipe orifice which is pushed onto a tail pipe of an exhaust system. The tail pipe orifice is connected only with the tail pipe, whereby a heat conduction exists from the heated tail pipe to the orifice. This orifice is therefore not suitable for fastening to rear covering parts, particularly when they are made of a plastic material and/or painted and/or coated.
It is therefore an object of the invention to provide a rear covering part with a tail pipe orifice which takes into account safety-related and visual aspects as well as styling and also prevents an excessive heating of the tail pipe orifice.
The principal advantages achieved by means of the invention are, in addition to an attractive appearance, that, in the event of a vehicle accident causing deformations on the rear covering part, the exhaust system with the tail pipe is protected to a certain extent from damage. This protection results from the tail pipe orifice, because of its correspondingly designed passage cross-section, being able to be pushed, for the most part over the tail pipe and, in the process, not significantly damaging the tail pipe. This particular fastening of the orifice and its extending through the rear covering part reduces the risk of leakage at the exhaust system. In addition, as a result of the corresponding passage cross-section, sufficient air is guided through the orifice during driving of the vehicle in order to keep this air at a low temperature or prevent an excessive convection, so that the gap between the orifice and the rear covering part can be optimized.
An improved cooling of the tail pipe orifice in the driving operation of the vehicle is achieved by means of a double-walled pipe for the orifice. Air is able to flow through the hollow jacket of this double-walled pipe, whereby, because of the thus achieved interior cooling air flow, the exterior pipe wall of the double-walled pipe is heat-insulated from the interior pipe wall along which the flow of the hot exhaust gases takes place.
It is a further object of the invention to provide fastening lugs which can be mounted on the exterior pipe wall of the orifice. These fastening lugs are connected with the rear covering part optionally by way of a fastening frame and are constructed in a strip shape, so that a punctiform linkage of the orifice to the rear covering part is achieved and little heat is transmitted to the rear covering part. For example, three fastening lugs may be used.
In a further development, in addition to the interior air flow through the hollow jacket around the tail pipe orifice, another, exterior cooling air flow can be guided past, which exits between the rear covering part and the tail pipe orifice, so that the exterior pipe wall of the tail pipe orifice is also cooled from the outside by the air which passes. Furthermore, the fastening lugs for the tail pipe orifice are situated in this exterior air flow, to provide cooling of these fastening lugs.
According to an another embodiment, the air outlet opening for the exterior air flow constructed between the tail pipe orifice and the rear covering part, for example, for appearance purposes, is advantageously equipped with a covering which may be provided with perforations.
A further preferred embodiment has the tail pipe orifice constructed as a double tail pipe orifice, in which case the two pipes may be fastened to one another and be disposed side-by-side or above one another.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.